Many chronic viral infections result in T cell exhaustion. Poor T cell function is associated with failure to contain HIV infection and collapse of T cell immunity precedes AIDS. Current antiretroviral therapies (ART) can contain HIV, but fail to fully eradicate the virus. Thus, achieving true cure of HIV remains a paramount goal. In 2008, Timothy Brown was effectively cured of HIV infection using a bone marrow (BM) transplant. The donor BM contained the ?32 mutation in CCR5 preventing HIV infection. Subsequent promising trials, while failing to achieve true cure, give impetus to improve upon, and understand the mechanisms of this HIV control using T cells engineered to resist infection. Thus, the main principle of this U19 is to test improved chemokine receptor- based HIV entry antagonists in engineered T cells in humans. Specifically, the HR2 C34 peptide fused to CXCR4 is a highly effective inhibitor of HIV entry that, in contrast to previous approaches, works at low molar ratios to inhibit HIV infection mediated by both CXCR4 and CCR5. Adaptive immunity is likely essential to the efficacy and sustainability of HIV cure even using infection resistant ACT. Thus, the central question of this project is to determine how dysfunction or ?exhaustion? of CD4 T cell responses is impacted by or can be prevented during ACT. T cell exhaustion is a common feature of many chronic infections including HIV and is defined by poor effector function, sustained and elevated expression of inhibitory receptors and an altered transcriptional program. A major question, therefore, is to what extent engineered, infection-resistant CD4 T cells become exhausted during ACT. Thus, we will test the hypothesis that molecular pathways associated with reduced exhaustion and effective CD4 T cell responses can be identified, monitored in ACT for HIV cure and that these pathways can serve as the foundation for rational improvement of next generation ACT approaches. To test this hypothesis, we propose the following Aims: SA1: To define the molecular pathways associated with persisting, functional virus-specific CD4 T cells during chronic viral infection. We hypothesize that virus-specific CD4 T cells with potent antiviral function, help activity and long-term persistence can be distinguished from those that are exhausted and unable to provide protection following HIV cure. SA2: To define the transcriptional program of engineered CD4 T cells following ACT for HIV cure. Here, we will test the hypothesis that C34:CXCR4 modified CD4 T cells will not undergo exhaustion in ACT for HIV. SA3: To directly test whether engineering CD4 T cells to resist exhaustion can enhance virus-specific CD4 T cell responses during chronic infection. We will test the hypothesis that specific CARs can deliver signals that enhance function and/or persistence of virus-specific CD4 T cell responses during chronic infection.